ES2636814T3 - Composite layers separated by phases and their applications - Google Patents

Abstract

A composite layer comprising: nano-cluster nodes and carbon nanoparticles arranged in a conjugated polymer matrix, in which the carbon nanoparticles are substantially separated from the phase of the conjugated polymer matrix forming laminar structures of carbon nanofibrils extending radially from the nanocluster nodes.

Description

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DESCRIPTION

Composite layers separated by phases and their applications Field

The present invention relates to nanocomposite films and, in particular, to nanocomposite films showing separate phase architectures.

Background

Thin organic films continue to be intensively researched for application in a variety of fields including organic light emitting devices (OLEDs), photovoltaic devices and organic photodetectors. The materials used to build organic optoelectronic devices are relatively cheap compared to their inorganic equivalents, thereby providing cost advantages over optoelectronic devices made of inorganic materials. In addition, organic materials provide desirable physical properties, such as mechanical flexibility, that allow constructions of unreachable devices with nigged crystalline materials.

Thin organic films, however, have performance disadvantages compared to crystalline inorganic materials. For example, some organic photovoltaic devices show efficiencies of 1% or less. The low efficiencies that are often shown in organic photovoltaic devices are the result of a severe scale discrepancy between the diffusion length of the exciton (Ld) and the thickness of the organic layer. The efficient absorption of visible electromagnetic radiation generally requires an organic film thickness of 500 nm or more. This thickness greatly exceeds the diffusion length of the exciton which is typically around 50 nm, often resulting in recombination of excitons. Given the disparity in performance, organic photovoltaic devices have encountered significant difficulties in challenging traditional inorganic devices.

Summary

In one aspect, composite layers are described that show separate phase architectures that, in some embodiments, can mitigate the performance disadvantages of previous organic layers of optoelectronic devices. An organic composite layer described here comprises nanocluster nodes and carbon nanoparticles arranged in a conjugated polymer matrix, in which the carbon nanoparticles are substantially separated from the phase of the conjugated polymer matrix forming lamellar structures of carbon nanofibrils around or which extend radially from the nanocluster nodes.

In some embodiments, for example, the carbon nanofibrils extend radially to a distance of at least 500 nm or at least 1 pm from the nanocluster nodes providing improved pathways for dissociation and transport of excitons.

In another aspect, photovoltaic devices are described here. A photovoltaic apparatus comprises a first and a second electrode and a photosensitive layer placed between the first and second electrode, the photosensitive layer comprising nanocluster nodes and carbon nanoparticles arranged in a conjugated polymeric matrix, in which the carbon nanoparticles are substantially separated phase of the conjugated polymeric matrix forming laminar structures of carbon nanofibrils around or extending radially from the nanocluster nodes.

In a further aspect, methods for producing composite layers are described. One method of producing a composite layer comprises mixing inorganic nanoparticles, conjugated polymeric phase and carbon nanoparticles in an organic solvent, adding inorganic nanoparticles in the conjugated polymeric phase to provide nanocluster nodes, and separating phase carbon nanoparticles from the phase. Polymeric conjugate in the form of laminar structures of carbon nanofibrils around or extending radially from the nanocluster nodes during removal of the organic solvent.

These and other embodiments are further described in the following detailed description.

Brief description of the drawings

Figure 1 is a transmission electron microscopy (TEM) image of a section of a composite layer according to an embodiment described herein.

Figure 2 is a TEM image of a section of a comparative layer formed by conjugated polymer and carbon nanoparticles not using nanocluster nodes.

Figures 3 (a) - (d) are TEM images of sections of composite layers according to some embodiments described herein.

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Figures 4 (a) - (c) are TEM images of sections of composite layers according to some embodiments described here.

Figure 5 is a histogram detailing the nanofibril thickness in response to the loading of inorganic nanoparticles in composite layers according to some embodiments described here.

Figures 6 (a) - (d) are TEM images of sections of composite layers according to some embodiments described here.

Figure 7 is a histogram detailing the nanofibril thickness in response to the rate of removal of organic solvent in composite layers according to some embodiments described herein.

Figures 8 (a) - (b) are current density graphs for photovoltaic devices that employ several layers of composite described here in relation to a comparative photovoltaic apparatus.

Figures 8 (c) - (d) illustrate the EQE and IQE of a photovoltaic apparatus that employs several layers of composite described here in relation to a comparative photovoltaic apparatus.

Figures 9 (a) - (b) are TEM images of sections of composite layers according to some embodiments described here.

Figure 9 (c) are TEM images of sections a composite layer in which inorganic nanoparticles are not present.

Detailed description

The embodiments described here can be more easily understood by reference to the following detailed description and examples and their previous and following descriptions. The elements, apparatus and methods described herein, however, are not limited to the specific embodiments presented in the detailed description and in the examples. It should be recognized that these embodiments are merely illustrative of the principles of the present invention. Numerous modifications and adaptations will be readily apparent to those skilled in the art without departing from the scope of the invention.

I. Composite layers

Aqm composite layers that show separate phase architectures are described. Such separate phase architectures, in some embodiments, can mitigate the performance disadvantages of previous organic layers of optoelectronic devices. For example, the separate phase architectures of composite layers described here can provide improved paths for the separation and collection of excitons in photovoltaic devices, thereby achieving improved efficiencies.

An organic composite layer described here comprises nanocluster nodes and carbon nanoparticles disposed in a conjugated polymeric matrix, in which the carbon nanoparticles are substantially separated from the phase of the conjugated polymeric matrix forming radially extending carbon nanofiber laminar structures. from the nanocluster nodes. Figure 1 is a TEM image of a section of a composite layer according to an embodiment described here. As illustrated in Figure 1, the composite layer section (10) comprises a cluster (11) of nanoparticles and laminar structures of carbon nanofibrils (12) that extend radially from the cluster (11) of nanoparticles. In the embodiment of Figure 1, the carbon nanofibrils (12) are formed of conjugated fullerene 1- (3-methoxycarbonyl) propyl-1-phenyl- (6,6) C61, (PCBM) separated from the matrix phase ( 13) Polymeric conjugated poly [4,4-didodecylpentalene [1,2-b] dithiophene-co-5-octyl-5H-thieno [3,4-c] pyrrole-4,6-dione. The carbon nanofibrils (12) extend outward from the nanocluster (11) distances well above 500 nm. In addition, the conjugated polymer matrix (13) can also form nanofibrils that alternate with carbon nanofibrils (12) in the laminar structure.

Turning now to the specific components, a composite layer described here comprises a conjugated polymer matrix. The conjugated polymer matrix may be formed by any conjugated polymer that functions to participate in the formation of laminar structures described herein. In some embodiments, for example, an appropriate conjugated polymer shows a lower surface energy than the nanoparticles that form the cluster of nanoparticles. In addition, the conjugated polymer matrix and carbon nanoparticles show a difference in surface energies sufficient to induce phase separation in the presence of nanocluster nodes. For example, in some embodiments, the conjugated polymer matrix exhibits a lower surface energy than carbon nanoparticles. As discussed further herein, the surface energies of the conjugated polymer can be altered and / or adapted by the presence of hydrophobic or hydrophilic side chains of the conjugated polymer.

In some embodiments, the conjugated polymer matrix may comprise polythiophenes, polythiophene derivatives or mixtures thereof. Polythiophene derivatives may include mono- or di-thiophenes coupled with thienopyrrole residues, benzoxadiazole residues or benzothiadiazole residues. In addition, polythiophenes can be provided chains

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hydrocarbon and / or alkoxide sides of appropriate length to adapt the surface power of the polymer for phase separation and / or interaction with carbon nanoparticles forming carbon nanofibrils. The conjugated polymer side chains can be linear, branched or cyclic and are generally made up of at least 10 carbon atoms. In some embodiments, the hydrocarbon side chains incorporate 12-20 carbon atoms. Table I provides several polythiophenes that can be used in the conjugated polymeric phase according to some of the present embodiments.

Table I - Polymerophenes of conjugated polymeric phase

Poly [4,4-didodecylpentalene [1,2-b] dithiophene-co-5-octyl-5H-thieno [3,4-c] pyrrole-4,6-dione Poly [4,8-bis (1-pentylhexyloxy) ) -benzo [1,2-b: 4,5-b0] dithiophene-2,6-diyl-alt-2,1,3-benzoxadiazol-4,7-diyl Poly (3-cyclohexyl-4-methylthiophene)

Poly (3-cyclohexylthiophene-2,5-diyl)

Poly (3-decyloxythiophene-2,5-diyl)

Poly (3-octylthiophene-2,5-diyl-co-3-decyloxythiophene-2,5-diyl)

Poly (3-decylthiophene-2,5-diyl)

Poly [(2,5-didecyloxy-1,4-phenylene) -alt- (2,5-thienylene)]

In addition, the conjugated polymer phase polythiophene may have a structure selected from formulas I and II below.

image 1

wherein R1, R2 and R3 are selected from the group consisting of C8-C20 alkyl, C8-C20 alkenyl, cycloalkyl, aryl, heteroaryl, alkylaryl, alkylheteroaryl and alkylcycloalkyl and R4, R5, R6 and R7 are selected from the group consisting of hydrogen, C4-C20 alkyl, C4-C20 alkenyl, cycloalkyl, aryl, heteroaryl, alkylaryl, alkylheteroaryl and alkylcycloalkyl.

The conjugated polymer matrix may also be formed by other conjugated or semiconductor polymers that show sufficient difference in surface energy with carbon nanoparticles or other electrically conductive nanoparticles to induce phase separation in the presence of nanocluster nodes. For example, the polymeric matrix may be formed by semiconductor polymers that include phenylenevinylenes, such as poly (phenylenevinylene) and poly (p-phenylenevinylene) (PPV), and their derivatives. In some embodiments, semiconductor polymers may comprise polyfluorenes, naphthalenes and their derivatives. In some embodiments, semiconductor polymers comprise poly (2-vinylpyridine) (P2VP), polyamides, poly (N-vinylcarbazole) (PVCZ), polypyrrole (PPy) and polyaniline (PAn). In some embodiments, a semiconductor polymer comprises poly [2,6- (4,4- bis- (2-ethylhexyl) -4H-cyclopenta [2,1-b; 3,4-b '] dithiophene) -alt-4 , 7- (2,1,3-benzothiadiazole)] (PCPDTBT).

As described herein, the conjugated polymer matrix may exhibit a lower surface energy than carbon nanoparticles, resulting in phase separation with carbon nanoparticles in the presence of nanocluster nodes. Hydrophobic or hydrophilic side chains can be used to modify the surface energy of the conjugated polymer matrix. For example, alkyl side chains or

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branched alkenyl to reduce the polar component of the surface energy of the conjugated polymer. In some embodiments, the appropriate conjugated polymeric matrices have a polar component that contributes 1% to 9% to the total surface energy of the polymer. In some embodiments, the polar component of the appropriate conjugated polymer contributes 1-5% of the total surface energy of the polymer.

The conjugated polymeric matrix may be present in the composite layer in any amount that is not incompatible with the objects of the present invention. The conjugated polymer matrix, for example, may be present in the composite layer in an amount of 20-80% by weight. In some embodiments, the conjugated polymer matrix is present in an amount of 30-70% by weight or 40-60% by weight.

As described herein, the nanocluster nodes are arranged in the conjugated polymer matrix. The nanocluster nodes can be formed from a material that has a higher surface energy than the conjugated polymer matrix that leads to the grouping of the material when it is contacted with the polymer matrix. The nanocluster nodes, for example, can be formed of inorganic nanoparticles. Higher surface energy of inorganic nanoparticles induces the aggregation of nanoparticles into nanoclusters in the conjugated polymer matrix. The inorganic nanoparticles may comprise metal nanoparticles, metal oxide nanoparticles, semiconductor nanoparticles or mixtures thereof. In some embodiments, the metal nanoparticles are transition metal nanoparticles. Additionally, the metal oxide nanoparticles may comprise transition metal oxides. Transition metal oxides may include oxides of metal elements of Groups IIB-VIB of the Periodic Table. Metal oxides can also include alkaline earth metal oxides. In some embodiments, for example, the metal oxide nanoparticles are ZnO and TiO2.

Like the conjugated polymer matrix, inorganic nanoparticles exhibit an appropriate surface energy to form the separate phase compositions described herein. In some embodiments, inorganic nanoparticles with an extremely high surface energy, such as silver oxide nanoparticles, prevent formation of lamella structures of separate phases. However, lower surface energy nanoparticles that include ZnO, TO2 and similar species are suitable for the separate phase compositions described herein.

The nanoparticles that form nanocluster nodes in the conjugated polymer matrix can have any size and shape that are not incompatible with the objects of the present invention. In some embodiments, the nanoparticles of a nanocluster have an average size ranging from 5-30 nm or 10-20 nm. In addition, the nanocluster nodes in the conjugated polymer matrix can have an average diameter of 100-500 nm. In addition, nanocluster nodes can show a variety of geometries that include spherical, elliptical or irregular shapes. The nanocluster nodes can generally be present in the conjugated polymer matrix in an amount of 0.1-10% by weight. In some embodiments, the nanocluster nodes are present in the conjugated polymer matrix in an amount of 0.5-5% by weight.

In addition to the nanocluster nodes, the carbon nanoparticles are also arranged in the polymer matrix, in which the carbon nanoparticles are separated from the phase of the conjugated polymer matrix that forms carbon nanofibrils that extend radially from the nanocluster nodes. In some embodiments, the appropriate carbon nanoparticles have a greater surface energy than the conjugated polymer matrix. In addition, the carbon nanoparticles and the conjugated polymer matrix show a difference in surface energies sufficient to induce phase separation in the presence of the nanocluster nodes.

Carbon nanoparticles, according to some embodiments, comprise fullerenes and fullerene derivatives. As shown here further, 1- (3-methoxycarbonyl) propyl-1-phenyl- (6,6) C61, (PCBM) can serve as carbon nanoparticles that form the separated phase nanofibrils. Other fullerene derivatives may include higher order fullerenes (C70 and higher) and endometalo-fullerenes (fullerenes that have at least one metal atom in them). Carbon nanoparticles can also comprise single-wall carbon nanotubes (SWNT), multi-wall carbon nanotubes (MWNT) or mixtures thereof. The surfaces of carbon nanoparticles can be modified with one or more side chains to adapt the surface energy of the nanoparticles for phase separation and / or interaction with the conjugated polymer phase.

Carbon nanoparticles are present in the conjugated polymer matrix in an amount sufficient to form the phase-separated carbon nanofibrils. In some embodiments, carbon nanoparticles are present in the conjugated polymer matrix in an amount of 20 to 80% by weight. Carbon nanoparticles may be present in the conjugated polymer matrix in an amount of 30 to 70% by weight or 35 to 65% by weight. In addition, carbon nanoparticles can be present in the conjugated polymer matrix in an amount of 50 to 66% by weight.

As described herein, the carbon nanoparticles phase is separated from the conjugated polymeric phase in the presence of the nanoclusters that form laminar structures of carbon nanofibrils with the conjugated polymeric phase. The nanofibrils can extend radially from the nanocluster nodes a considerable distance or length within the conjugated polymer matrix. In some embodiments, the nanofibrils are

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They extend radially a distance of at least 1 pm from one or more nanocluster nodes. Carbon nanofibrils, in some embodiments, extend radially a distance from a nanocluster node, to a distance provided in Table II.

Table II - Distance or length of carbon nanofibrils (pm)

image2

In addition to the length, the separate phase carbon nanofibrils can show various thicknesses. For example, carbon nanofibrils can have thicknesses ranging from 5 to 30 nm. In some embodiments, the carbon nanofibrils have thicknesses of 10 to 20 nm or 10 to 15 nm. As discussed below, the thickness of the carbon nanofibrils can be controlled by one or more processing conditions of the composite layer.

In some embodiments, the carbon nanoparticles can be replaced by one or more species of inorganic nanoparticles to form inorganic conductive or semiconductor nanofibrils that extend radially from the nanocluster nodes in the conjugated polymer matrix. For example, inorganic nanoparticles showing differences in surface energy with the polymer conjugate matrix sufficient to induce phase separation in electrically conductive nanofibrils in the presence of nanocluster nodes can be used. In some embodiments such nanoparticles comprise semiconductor nanoparticles, which include semiconductor nanoparticles III / V and / or II / VI or quantum dots. In addition, inorganic nanoparticles can comprise metal nanoparticles, which include transition metal nanoparticles.

II. Photovoltaic devices

In another aspect, photovoltaic devices are described here. A photovoltaic apparatus comprises a first and a second electrode and a photosensitive layer placed between the first and the second electrode, the photosensitive layer comprising nanocluster nodes and carbon nanoparticles disposed in a conjugated polymeric matrix, in which the carbon nanoparticles are substantially phase separated from the conjugated polymer matrix forming laminar structures of carbon nanofibrils that extend radially from the nanocluster nodes.

Turning now to the specific components, the photovoltaic apparatus comprises a first and a second electrode. The first and second electrode may be formed of any electrically conductive material that is not incompatible with the objectives of the present invention. The first and second electrode, for example, may be formed of metal or alloy, including aluminum or transition metals or alloys. In some embodiments, one or both of the first and second electrodes are radiation transmitters. A radiation transmitting electrode may be formed by a conductive radiation transmitting oxide. The radiation transmitting conductive oxides, in some embodiments, may comprise indium tin oxide (ITO), gallium indium stannous oxide (GITO) or zinc indium tin oxide (ZITO). In another embodiment, a radiation transmitting electrode may comprise a radiation transmitting polymeric material such as polyaniline (PANI) and its chemical relatives. In some embodiments, 3,4-polyethylenedioxythiophene (PEDOT) may be a polymeric radiation transmitting material suitable for the first and / or second electrode. In other embodiments, a radiation transmitting electrode may comprise a metal or carbon nanotube layer having a thickness that functions to at least partially allow visible electromagnetic radiation to pass through.

In addition to the first and a second electrode, the photovoltaic apparatus described herein comprises a photosensitive layer comprising nanocluster nodes and carbon nanoparticles arranged in a conjugated polymer matrix, in which the carbon nanoparticles are substantially separated from the phase of the conjugated polymer matrix. forming laminar structures of carbon nanofibrils that extend radially from the nanocluster nodes. The components of the photosensitive layer, which include the nanocluster nodes, conjugated polymer matrix and carbon nanoparticles, can have composition parameters and / or properties

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described for them in Section I above. In addition, carbon nanofibrils formed by phase separation of the carbon nanoparticles of the conjugated polymeric matrix may have any of the properties described in Section I.

The conjugated polymeric matrix of the photosensitive layer can show various absorption profiles of electromagnetic radiation. The conjugated polymer, for example, can be selected to have maximum absorption in the visible region of the electromagnetic spectrum. In some embodiments, the conjugated polymer can also absorb wavelengths in the ultraviolet and / or infrared regions of the spectrum. The excitons are generated in the photosensitive layer by radiation absorption by the conjugated polymeric phase. In addition, exciton dissociation can be precipitated into heterojunctions formed between the conjugated polymer matrix and the carbon nanofibrils of the photosensitive layer. The conjugated polymer matrix, for example, serves as a donor material and carbon nanofibrils serve as an acceptor material, thereby forming heterojunctions that function for the separation of excitons into holes and electrons.

Given its structure over long distances, the carbon nanofibrils of the photosensitive layer facilitate the transport of cargo, thereby improving the collection of charge and the efficiency of the photovoltaic apparatus. In addition, the photosensitive layer can be made thicker to obtain improved absorption characteristics due to the extended structure of carbon nanofibrils. For example, the photosensitive layer may have a thickness of 200 nm at 1 pm. In some embodiments, the photosensitive organic layer has a thickness greater than 1 pm.

The photovoltaic apparatus described herein may additionally comprise additional layers such as one or more exciton blocking layers. An exciton blocking layer (EBL) can act to confine photogenerated excitons in the region near the dissociation interface and prevent parasitic cooling of excitons at a photosensitive layer / electrode interface. In addition to limiting the path on which excitons can diffuse, an EBL can additionally act as a diffusion barrier for substances introduced during electrode deposition. In some embodiments, an EBL may be thick enough to fill holes or short circuit defects that would otherwise render an organic photovoltaic device inoperable.

An EBL may comprise a polymeric material such as polyethylenedioxythiophene-polystyrene sulfonate (PEDOT: PSS). Alternatively, an EBL may comprise a composite material. For example, an EBL may comprise carbon nanoparticles dispersed in 3,4-polyethylenedioxythiophene: polystyrene sulfonate (PEDOT: PSS). In another embodiment, an EBL comprises carbon nanoparticles dispersed in polyvinylidene chloride and / or its copolymers. In further embodiments, the EBLs may comprise any polymer having an operable work function energy to allow the transport of holes while preventing the passage of electrons. In some embodiments, an EBL may be disposed between the anode and the photosensitive layer of the photovoltaic apparatus.

Additionally, one or more layers of metal oxide can be introduced into the photovoltaic architecture. For example, a layer of Li2O and / or MoO3 can be placed between the photosensitive layer and the cathode. Alternatively, a layer of LiF can be placed between the photosensitive layer and the cathode.

The electrodes of the photovoltaic apparatus, in some embodiments, can serve as support (s) for the photosensitive layer. Alternatively, the photovoltaic construction may be supported by an external substrate. Appropriate external substrates can be flat or curved. In some embodiments, an external support substrate comprises a flat sheet of glass or plastic. In addition, an external substrate may have a cylindrical geometry. A cylindrical substrate can be a tube or fiber, such as an optical fiber. In embodiments where the support is an optical fiber, electromagnetic radiation can be supplied to the photosensitive layer from inside the fiber and / or fiber sides. In tubular constructions, several liquids can be flowed through the interior of the tube for the collection of thermal energy. Optical fiber and tubular substrates are described in greater detail in US patent application serial numbers 12 / 298,942 and 13 / 880,310, respectively.

As described here, carbon nanofibrils can provide improved paths for the separation and collection of excitons in photovoltaic devices, thus achieving improved efficiencies. For example, a photovoltaic apparatus described here, in some embodiments, may show an external quantum efficiency (EQE) greater than 20% at one or more wavelengths in the visible spectrum. In some embodiments, a photovoltaic apparatus described here shows EQE of 20-25% at one or more other wavelengths in the visible spectrum.

III. Production methods of composite layers

In a further aspect, methods for producing composite layers are described. A method of producing a composite layer comprises the mixing of inorganic nanoparticles, conjugated polymeric phase and carbon nanoparticles in an organic solvent, the addition of inorganic nanoparticles in the conjugated polymeric phase to provide nanocluster nodes and the phase separation of the Carbon nanoparticles of the conjugated polymer phase in the form of laminar structures of carbon nanofibrils that extend radially from the nanocluster nodes during removal of the organic solvent.

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The components of the methods described herein, which include the inorganic nanoparticles, the conjugated polymeric phase and the carbon nanoparticles, may have composition parameters and / or properties described therein in Section I above. For example, inorganic nanoparticles may comprise transition metal oxide nanoparticles while the conjugated polymeric phase is formed by a polythiophene listed in Table I above, and carbon nanoparticles may comprise fullerenes or fullerene derivatives. In addition, the nanofibrils formed by phase separation of the carbon nanoparticles of the conjugated polymeric phase may have any of the properties described in this Section I.

As discussed further here, the thickness of the phase separated carbon nanofibrils can be altered depending on various processing conditions, including the rate of removal of the organic solvent. For example, the thickness of nanofiber can be inversely proportional to the speed of solvent removal that provides the ability to adapt separate phase architectures of the composite layer. The solvent removal rate can be varied using organic solvents of different vapor pressure and / or the use of different drying temperatures. In some embodiments, the additive (s) can be combined with organic solvent to alter the vapor pressure of the solvent, producing the desired drying speed and nanofibril morphology.

These and other embodiments are further illustrated by the following non-limiting examples.

Example 1 - Composite Layer

A composite layer was formed providing a mixture of zinc oxide (ZnO) nanoparticles (10-20 nm), PCBM and conjugated polymer of poly [4,4-didodecylpentalene [1,2-b] dithiophene-co-5- Octyl-5H-thieno [3,4-c] pyrrole-4,6-dione in chlorobenzene as solvent. The conjugated polymer and PCBM were present in the mixture with a ratio of 1: 1 (polymer: PCBM). In addition, the ZnO nanoparticles were present in an amount sufficient to achieve about 1.5% by weight of charge in the final composite layer. The mixture was deposited on a copper grid substrate by centrifugal molding, and the chlorobenzene solvent was removed by drying.

The resulting composite layer is illustrated in the view of the TEM section of Figure 1. As illustrated in Figure 1, the composite layer section (10) comprises a cluster (11) of nanoparticles and nanofiber laminar structures (12) carbon and nanofibrils (13) of conjugated polymer that extend radially from the cluster (11) of nanoparticles. In the embodiment of Figure 1, the carbon nanofibrils (12) are formed by a conjugated fullerene phase 1- (3-methoxycarbonyl) propyl-1-phenyl- (6.6) C61, (PCBM) separated from the phase of the nanofibrils (13) of the matrix of poly [4,4-didodecylpentalene [1,2-b] dithiophene-co-5-octyl-5H-thieno [3,4-c] pyrrole-4,6-dione. The carbon nanofibrils (12) extend outward from the nanocluster (11) distances well above 500 nm.

A comparative layer was produced in a substantially identical manner, the difference being the absence of ZnO nanoparticles in the mixture. As shown in Figure 2, the resulting layer showed no specific architecture of separate phases and resembled previous organic films incorporating PCBM.

Example 2 - Composite Layer

A composite layer was formed according to the protocol of Example 1, the difference being that ZnO nanoparticles were present in an amount sufficient to achieve about 0.75% by weight of charge in the final composite layer. Figures 9 (a) and 9 (b) are TEM images of a section of the resulting composite layer with different magnifications. The scale bar in Figure 9 (a) is 500 nm, and the scale bar in Figure 9 (b) is 2 pm. As illustrated in Figure 9 (b), carbon nanofibrils extend from the cluster of ZnO nanoparticles distances of the order of micrometers. For comparison purposes, a composite layer was prepared according to Example 1, in which ZnO nanoparticles were not used. The absence of ZnO nanoparticles prevented the formation of lamella structures as shown in the TEM of Figure 9 (c).

Example 3 - Composite Layer

A composite layer was formed according to the protocol of Example 1, the difference being that the ZnO nanoparticles were replaced with TiO2 nanoparticles (10-20 nm). The resulting composite layer showed laminar structures of carbon nanofibrils that extend radially from nanocluster nodes, similar to those shown in Figure 1.

Example 4 - Loading of PCBM in the composite layer

Composite layers 3-6 were produced according to Example 1, in which the load of PCBM in the composite layer was increased to provide the conjugated polymer ratios: PCBM of Table III.

TABLE III - Poor relationships of the composite layer: PCBM.

 Composite layer

 Polymer conjugate ratio: PCBM Figure

 3

 1: 1 3 (a)

 4

 1: 2 3 (b)

 5

 1: 3 3 (c)

 6

 1: 4 3 (d)

As illustrated in Figures 3 (a) - (d), phase separated carbon nanofibrils are easily formed at 5 ratios of 1: 1 and 1: 2. At higher ratios of 1: 3 and 1: 4, the PCBM begins to crystallize in large clusters losing the morphology of the nanofibrils near the nanoclusters. It was observed, however, that for a 1: 4 ratio, the nanofibril morphology was restored in regions distant from the nanocluster nodes [Figure 3 (d)].

Example 5 - Loading of inorganic nanoparticles in the composite layer

10 Composite layers 7-9 were produced according to Example 1, in which the loading of the ZnO nanoparticles varied according to Table IV, and the ratio of conjugated polymer: PCBM was kept constant at 1: 2 for each composite layer .

Table IV - Loads of inorganic nanoparticles of the composite layer

 Composite layer

 ZnO nanoparticle load (% by weight) Figure

 7

 5 4 (a)

 8

 2.5 4 (b)

 9

 1.2 4 (c)

As illustrated in Figures 4 (a) - (c), the increased loading of ZnO nanoparticles increased the nanocluster size, which contributed to the thickness distribution of conjugated polymer / carbon nanofibril as provided in Figure 5. As provided in Figure 5, the particle size of the nanocluster varied from 148 nm to 799 nm. A statistical study of the thickness of conjugated polymer / nanofibril of PCBM extending from different nanocluster node sizes indicated that the fibril samples showed a typical Gaussian distribution of a random path process. Smaller nanoclusters, for example, produced nanofibrils of reduced thickness (for example, 10 nm) while larger nanoclusters produced nanofibrils are up to 25 nm thick.

Example 6 - Solvent removal rate

Composite layers 10-13 were produced according to Example 1, the difference being the alteration of the CB 25 solvent as detailed in Table V.

TABLE V - Solvent composition parameters

 Composite layer

 Organic solvent composition Figure

 10

 1,2-dichlorobenzene (DCB) / chlorobenzene (CB) 6 (a)

 eleven

 DCB / CB and 1% by volume of 1-chloronaphthalene (CN) 6 (b)

 12

 DCB / CB and 2% by volume of CN 6 (c)

 13

 DCB / CB and 6% by volume of CN 6 (d)

As shown in the histogram of Figure 7, the standard deviation of the four organic solvent systems was similar to judging by the shape of the curves. However, the expected value shifts from 10-12 nm

for the DCB / CB solvent of the centrifugal molding form of fast-drying film at 14-15 nm for composite layers molded in DCB / CB / 2% by volume of CN and up to 16-18 nm for composite layers molded in DCB / CB / 6% by volume of CN.

Example 7 - Photovoltaic device

5 Photovoltaic devices that have the construction listed in Table VI were built on ITO substrates. PEDOT: PSS EBLs were deposited on ITO substrates by centrifugal molding to a thickness of about 80 nm. The photosensitive layers produced according to Example 1 were deposited on the EBLs by centrifugal molding to a thickness of 1O0 nm. The conjugated polymer of the photosensitive layers was poly [4,4-didodecylpentalene [1,2-b] dithiophene-co-5-octyl-5H-thieno [3,4-c] pyrrole-4,6-dione (PI) and the carbon nanoparticles were 10 PCBM. The ratio of P1: PCBM was 1: 2. If present, the inorganic nanoparticles that form nanoclusters were ZnO. MoO3 and Al were deposited on the photosensitive layer.

Table VI - Construction of the photovoltaic device

 Photovoltaic device

 EBL anode Photosensitive layer Metal oxide layer Catodo

 1 (comparative)

 ITO PEDOT: PSS P1: PCBM (1: 2) MoO3 Al

 2

 ITO PEDOT: PSS P1: PCBM (1: 2) and 0.1% by weight of ZnO MoO3 Al nanoparticles

 3

 ITO PEDOT: PSS P1: PCBM (1: 2) and 0.3% by weight of ZnO MoO3 Al nanoparticles

 4

 ITO PEDOT: PSS P1: PCBM (1: 2) and 0.6% by weight of ZnO MoO3 Al nanoparticles

 5

 ITO PEDOT: PSS P1: PCBM (1: 2) and 1.2% by weight of ZnO MoO3 Al nanoparticles

 6

 ITO PEDOT: PSS P1: PCBM (1: 2) and 2.5% by weight of ZnO MoO3 Al nanoparticles

The photovoltaic apparatus of Table VI was subsequently tested to determine the current density, EQE 15 and IQE after exposure to radiation in the visible region of the electromagnetic spectrum. The results are provided in Figures 8 (a) - (d). As illustrated in Figures 8 (a) and (b), the current densities for photovoltaic devices employing composite layers described herein comprising separate phase laminar structures of carbon nanofibrils are substantially higher than the comparative photovoltaic apparatus of P1 photosensitive layer: PCBM. In addition, the EQE and the IQE for the photovoltaic device that uses composite layers described here are 20-92% higher than the comparative photovoltaic device.

Example 8 - Photovoltaic device

Photovoltaic devices were produced having the construction of Table VI, the difference being that the conjugated polymer of the photosensitive layer was changed to poly [4,8-bis (1-pentylhexyloxy) -benzo [1,2-b: 4, 5-b0] dithiophene-2,6-diyl-alt-2,1,3-benzoxadiazol-4,7-diyl. The photovoltaic devices were tested to determine the current density, EQE 25 and IQE after exposure to radiation in the visible region of the electromagnetic spectrum. The test results were similar to those detailed in Example 7.

Several embodiments of the invention have been described in compliance with the various objectives of the invention. It should be recognized that these embodiments are merely illustrative of the principles of the present invention. Numerous modifications and adaptations thereof will be readily apparent to those skilled in the art 30 without departing from the scope of the invention.

Claims (20)

5 10 fifteen twenty 25 30 35 40 Four. Five 1. A composite layer comprising: nanocluster nodes and carbon nanoparticles arranged in a conjugated polymer matrix, in which the carbon nanoparticles are substantially separated from the phase of the conjugated polymer matrix forming laminar structures of carbon nanofibrils that extend radially from the nanocluster nodes. 2. The composite layer of claim 1, wherein the carbon nanofibrils are 5-25 nm thick. 3. The composite layer of claim 1, wherein the carbon nanofibrils extend radially a distance of 500 nm to 5 pm from the nanocluster nodes. 4. The composite layer of claim 1, wherein the carbon nanofibrils extend radially a distance of at least 1 pm from the nanocluster nodes. 5. The composite layer of claim 1, wherein the nanocluster nodes are formed of a material having a surface energy greater than that of the conjugated polymeric matrix and carbon nanoparticles. 6. The composite layer of claim 1, wherein the nanocluster nodes are formed of inorganic nanoparticles. 7. The composite layer of claim 5, wherein the inorganic nanoparticles comprise metal nanoparticles or metal oxide. 8. The composite layer of claim 1, wherein the nanocluster nodes have a diameter of 100500 nm. 9. The composite layer of claim 1, wherein the carbon nanoparticles and the conjugated polymer matrix show a sufficient surface energy difference to induce phase separation in the presence of the nanocluster nodes. 10. The composite layer of claim 1, wherein the carbon nanoparticles comprise PCBM. 11. The composite layer of claim 1, wherein the carbon nanoparticles are present in the layer in an amount sufficient to form the carbon nanofibrils. 12. The composite layer of claim 1, wherein the carbon nanoparticles are present in an amount of 30-66 percent by weight of the composite layer. 13. The composite layer of claim 1, wherein the nanoclusters are present in an amount of 0.5 to 5 percent by weight of the composite layer. 14. A photovoltaic apparatus comprising: first and second electrode; Y a photosensitive layer placed between the first and second electrode, the photosensitive layer being a composite layer according to claim 1. 15. The photovoltaic apparatus of claim 14, wherein the composite layer is as claimed in any of claims 2-8. 16. The photovoltaic apparatus of claim 14, wherein the photosensitive layer is 300 nm thick at 1 pm. 17. A method of producing a composite layer according to claim 1, comprising: mixing inorganic nanoparticles, conjugated polymeric phase and carbon nanoparticles in an organic solvent; adding inorganic nanoparticles in the conjugated polymeric phase to provide nanocluster nodes; Y phase-separating carbon nanoparticles from the conjugated polymeric phase in the form of laminar structures of carbon nanofibrils that extend radially from the nanocluster nodes during removal of the organic solvent. 18. The method of claim 17, wherein the composite layer produced is a composite layer according to any one of claims 3, 4, or 9. 19. The method of claim 17, wherein the inorganic nanoparticles comprise metal or metal oxide. The method of claim 17 further comprising altering the thickness of the nanofibrils of carbon altering the removal rate of organic solvent. 21. The method of claim 20, wherein the thickness of the carbon nanofibrils is inversely proportional to the rate of removal of the organic solvent.